This invention relates to window shades, shower curtains and other sheet material products that are formed of accordion folded laminates of fiber reinforced by thermoplastic film, such as polyester film, with an adhesive dispersed between the layers of the laminate, such as low melt polyester adhesive powder. Window shades and shower curtains formed of the accordion folded laminate tend to hold their shape so that the folds do not tend to disappear under the weight of the window shade, and the laminate tends to resume a folded configuration after having been extended.
Accordion folded sheet material has been extensively used in the past as decorative curtains and other items having the folds extending vertically, and also as window shades and similar items that have the folds extending horizontally. The sheet material which is formed in the folded configuration has included various decorative patterns on its surface and provides a very pleasing visual effect. There is a history of using stand-alone panels of resin-stiffened fabric. This fabric has traditionally been polyester (only). This fabric may have been woven, knitted, or non-woven (such as "stitch-bonded" non-woven). The yarns may have been spun staple or continuous filament yarns. The resin-stiffened fabrics may have been finished with either thermoplastic or thermoset resins or combinations of both types of resins. The resins have generally been selected from acrylic or melamine resins.
The potential use of accordion folded sheets seems to be limitless; however, when the sheet material is stretched from a compact accordion fold configuration to an expanded configuration, the folds tend to lose their shapes and become less attractive. This is particularly true with accordion folded window shades and similar items that have their folds extending horizontally. The weight of the lower portion of the window shade sheet material is applied to the upper portion thereof and tends to stretch the accordion folds at the upper portion out to a substantially flat configuration. When in this configuration, the upper portion of a window shade tends to lose its accordion folded identification and appears more nearly in a flat configuration, such that the pattern of the overall shade is not very attractive. Further, the relatively weak folds of the typical accordion folded fabric tends to permit the folds to become everted, which further detracts from the visual appearance of the material.
In many cases it is desirable that the folds of an accordion folded sheet material be maintained in a substantially uniform fold configuration across the entire length or width of the sheet material. This not only provides a uniformity of folds but also tends to present the pattern on the surface of the sheet material in a uniform manner. For example, if a pattern on the surface of the sheet material has a uniform repeat of a visual design and the folds of the accordion folded sheet are not uniformly open, the pattern will not be uniformly presented.